Generally, a display is used in such an environment that is entered by outside light, whether it is used indoors or outdoors. Incident light, such as external light, is specularly reflected on the surface of the display or the like, and such a reflected image that is caused by this specular reflection is mixed with an image which is displayed in the display, thereby decreasing screen display quality. Therefore, providing an antireflection function is essential to the surface of the display or the like. This antireflection function is required to have more enhanced performance and be combined with other functions.
Generally, an antireflection function is obtained by forming antireflection layers of a multilayer structure on a transparent substrate, or specifically, by forming, on a transparent substrate, antireflection layers having a repeated structure of a high refractive index layer and a low refractive index layer each of which is made of a transparent substrate, such as metal oxide. The antireflection layers configured by a multilayer structure can be formed by using a dry deposition method, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD).
The dry deposition method has an advantage of finely controlling the thickness of a low refractive index layer and a high refractive index layer. On the other hand, the dry deposition method, in which deposition is performed in vacuum, suffers from a problem of low productivity and unsuitableness to mass production. For this reason, attention is drawn to a wet deposition method as a method of forming antireflection layers. The wet deposition method uses a coating liquid and enables increase of area, continuous production and cost reduction.
An antireflection film in which these antireflection layers are provided on a transparent substrate has a comparatively soft surface. Therefore, in order to give surface hardness to the film, the film is provided with a hard coating layer in the manufacturing process, followed by forming antireflection layers thereon, the hard coating layer being generally obtained by curing an ionizing-radiation-curable material, such as an acrylic material. A hard coating layer made of an acrylic material has high surface hardness, glossiness, transparency and abrasion resistance. An antireflection film manufactured by coating at least a low refractive index layer on such a hard coating layer has a merit of being manufactured at comparatively low cost and thus is widely available on the market.
Techniques related to the technique mentioned above are disclosed, for example, in JP-A-2005-202389, JP-A-2005-199707, JP-A-H11-092750, JP-A-2007-121993, JP-A-2005-144849, JP-A-2006-159415 and JP-A-2010-217873.